On Monday 09 September 2013 17:10:25 Martin Graesslin wrote: > On Monday 09 September 2013 16:48:05 David Faure wrote: > > On Monday 09 September 2013 14:23:10 Sebastian Kügler wrote: > > > Martin Grässlin asked if we could offer an async API for this. Opinions? > > > > This task is mostly I/O, and a bit of CPU. > > Portable async I/O requires doing it in a thread. > > To avoid setting up a thread every time, this could use QThreadPool (but a > > dedicated one, to avoid blocking the main one which is supposed to be > > about > > pure-CPU operations only), and the runnable would call the sync trader > > API. > > > > So, it's feasible. > > But is it worth it? > > Just adding the reasoning why I suggested it. We tried (in KWin) to move all > the querying to a thread. It utterly failed due to KGlobal not being thread > safe. The code is still there, so I will probably switch with frameworks 5. > > In KWin all the plugin loading is during start up, but none of them is > essential. By making it async we can significantly improve the startup time > - that is the time till the first frame is rendered and the splash screen > unfreezes.
Ah, but you say "plugin loading", not just "locating plugins" (which was what my previous email was about). Surely loading (which means creating the objects in the plugin) in a secondary thread requires a lot of extra care. The plugin authors won't expect that, they'll create QObjects, which will then live in the wrong thread -- or there will be races with the init in the main thread... > Finding a large number of plugins at startup is - I assume - relevant to > many applications, for example Plasma. If we have the API in a way that it > makes async usage easy I think it would help a lot and sync usage is still > possible: .waitForFinished(). If the app wants to actually load plugins in a thread, it needs to manage that thread. It's not just a one-time task with a result, like locating plugins and returning a QStringList or so. It's now a longer-living thread, with synchronization issues. These large apps can do the plugin loading in a thread, but they'll have to handle the synchronization issues. I don't see a way to encapsulate all of it, it sounds rather dangerous (apps will not use proper synchronization then). The difference with KDE4 is that there's no KGlobal anymore :) So now what you tried should be possible. -- David Faure, fa...@kde.org, http://www.davidfaure.fr Working on KDE, in particular KDE Frameworks 5 _______________________________________________ Kde-frameworks-devel mailing list Kde-frameworks-devel@kde.org https://mail.kde.org/mailman/listinfo/kde-frameworks-devel
